Renamed 'unstable' to 'beta'.

Our dev processes are pretty darn good now, and we have a lot more
eyes on code. I'd like to change `unstable` releases to `beta` releases.
(It's good enough for Google and Squad!)
Merge pull request #594 from pjf/beta_than_anything

Renamed 'unstable' to 'beta'.
Try to fix the missing default instance bug
Copy downloads before iterating over them, since they may be modified concurrently.

Without this fix I repeatably see 'System.InvalidOperationException: Collection was modified; enumeration operation may not execute.' exceptions while installing KarbonitePlus.
Merge pull request #601 from cswetenham/master

Copy downloads before iterating, since they may be modified concurrently
Merge pull request #600 from AlexanderDzhoganov/master

Fix the missing default instance bug
Change PortableDir to use GetExecutingAssembly instead of GetEntryAssembly. The later can fail in certain types of test runner.
Add equals and hashcode to KSP.
Based on the gamedir.
Reworked KSPManager.
Extracted the registry functions to their own interface. Added tests.
Fixes #602.
Merge branch 'release-v1.2'

* release-v1.2:
  Renamed 'unstable' to 'beta'.
Merge pull request #607 from RichardLake/#602

Fixes: Gui shows non-updateable mods as having a update #602
Relationship resolver now uses KSP version in resolution.

`LatestAvailableWithProvides` now requires a mandatory KSP version, so
we don't accidentally do this again.
CKAN.dll: LatestAvailable now requires a version number

This means we can never go looking up mods which may be the wrong
version for our install by accident. It may also fix some edge cases
like #602 where we may show the wrong versions being available.

Most of the changes in this commit are to the test cases, which now
require the mandatory argument. :)

Tested that this closes #610 with our NEAR test example.
Merge pull request #611 from pjf/610_relationship_resolver

Bugfix: Always use current KSP version when resolving relationships
Small GUI ModList touch-ups

- Latest version now displayed properly
- Removed KSP version column
Merge pull request #614 from AlexanderDzhoganov/master

Small GUI ModList touch-ups
Re-enabled repository selection for the GUI
Merge pull request #615 from AlexanderDzhoganov/master

Re-enabled repository selection for the GUI
Added Net.UserAgentString which all WebClients will use