Add copy to text items in pcbnew. Automatically mirror text items added to back silkscreen (bug 1017446).

Coordinates were using always 3 digits (1/1000 inch  for mantissa). Uses now 4 digits max in inches and 3 digits max in mm
The resolution is therefore 1/10000 inch or 1/1000 mm. Note this is a limitation of Excellon format.

When reading board files, the net 0 was stored twice.
It creates only log messges in debug mode, because the list of nets is rebuild after reading files.

Use now English layers names to build filenames in plot functions (for techical layers), because translated names create sometimes problems in filenames.
(should do not change anything for English users)
Fix compil issue under wxGTK 2.8.12, created by my recent commit.
Minor changes to make translations easier.

Use now English layers names to build filenames in plot functions (for techical layers), because translated names create sometimes  problems in filenames.
(should do not change anything for English users)

Code cleaning in autoroute functions.

Commit JP's custom page size fix for Pcbnew s-expressions file format with minor changes.  Thanks JP.

All: fix a truncation issue in ReturnValueFromString that creates sometimes a small error for values entered in dialogs.
Pcbnew: fix a compatibility issue with nano version for zones parameters.

* Put text effects on a single line.
* Remove size token when defining drill sizes.
* Don't save net in pad definition when pad has no connection.

Fix an issue (only found using gcc under mingw) in dsnlexer.cpp, using ::isspace( ) function that accepts only a 7 bit ASCII value under gcc/ mingw.

Very minor other fixes.

DIMENSION::m_Value not being saved in LEGACY_PLUGIN using scaling, DIMENSION::AdjustDimensionDetails() uses arrowz appropriate to build

autoroute functions: code cleaning

* Use index when saving layers to handle translated layer names.
* Add LOCALE_IO switcher when loading s-expression format.
* Make SEGVIA default to through hole to improve file size.
* Don't save default orientation of 0 degrees in TEXTE_MODULE and TEXTE_PCB.
* Don't save default zone configuration parameters.
* Save multiple zone corners on a single line.
* Fixed missing ( check in graphic and module arc parsers.
* Consistency improvements for DRAWSEGMENT and EDGE_MODULE objects.
* Minor tweaks to D_PAD formatting.

Pcbnew: automatic selection of plugin when loading a file with .kicad_pcb extension from history list.
Very minor other fixes

fix incorrect use of KIROUND instead of KiROUND in parseBoardUnits( const char* aExpected ) (see comments in .h file)
very minor fix in pcb_parser.cpp
Fix scaling issue with nanometers in gpcb footprint import.

* Change save order of drawings to match legacy file format object order.
* Set end point of SEGVIA to start point so the round trip back to legacy
  format is the same.
* Fixed bug saving and loading oval pad drill parameters.
* Fixed bug saving and loading rectangular pad deltas.
* Fixed missing layer for PCB_TARGET.
* Fixed EDA_TEXT italic bug.  Thanks Dick!
* Remove some left over debug logging statements.

Pcbnew: fix issue about order of tracks this order was modified when reading and writing a board, even without any change in board.
Fix compil warnings and wx28 compatibility.
code cleaning in autoroute functions.

* Apply Dick's patch along with a few minor changes to fix some clashes with
  changes in my branch.  Thanks Dick!
* Added missing DRAWSEGMENT line angle.
* Fix thru hole pad layer mask issue.

Some code cleaning in autoroute functions.

Tracks should be loaded in the same order as they were saved, no exceptions.
This is for the version control system user.
But even with this objective now implemented in LEGACY_PLUGIN, the TRACKS
are still going through a food processor after they are loaded, and the poor
version control system user has no relief, even with this patch.

TRACKS are always modified after being loaded, and I think this needs to be fixed still.

* Add s-expression file parser object and keyword files.
* Fix minor issues with s-expression file formatting.
* Fix a minor bug the zone container fill state parsing in the legacy plugin.
* Move EDA_TEXT visibility definition to eda_text.h.
* Add minor BOARD_ITEM object improvements to support s-expression file
  parser.

Minor code cleaning in autoroute files.