Use latest OxyPlot version. Declare user agent to OpenStreetMaps

#36 Supports selection of Decimal Separator.

Retain settings on upgrade (#38)

Backup and restore setting and plugins when application is auto-upgraded.
Overwrite old StandardPanels.dll after update to replace with new version.

Merge c900b66 into edea235

Merge d250d77 into edea235

User choice of pre-release

Added checkbox in about to select to update to pre-releases.

Fixed Map axis labels

Merge d250d77 into edea235

Fix Squirrel Auto updater(#32)

* Since standard behavior is fine remove Squirrel awareness

* Handle firstrun without Squirrel

* Downgraded SharpCompress and Cecil

See Squirrel/Squirrel.Windows#1253

* Restart after updater disposed

This should fix leaked mutex errror

Fix squirrel by upgrading all dependencies to latest (#31)

* Upgrade framework to 4.6.1 for TLS 1.2 support
* Updated dependent libs and frameworks
* Fixed build script paths