Simplify build by removing GC tweaking logic

Mono 3.0.x was the first version when Mono's SGEN GC could be
considered stable, and F# was using it by default for this
version.

But then Mono 3.2.0 was released, which defaults to SGEN GC
anyway, so there's no need to tweak F# build or scripts anymore,
as we can simplify all this by just making F# use what the
underlying mono uses as default.

If some user is interested in using SGEN GC, she should just
make sure that she's using Mono 3.2.x or higher, or just adjust
MONO_ENV_OPTIONS env var herself.
Added Shared Unit test files
Added Android Tests
Added C# Android Wrapper

Due to a resource generation issue in F# Android the tests have to be
wrapped by C# for now.
See https://bugzilla.xamarin.com/show_bug.cgi?id=17390
Added iOS Tests
Added Solution file
Updated .gitignore
Merge pull request #247 from 7sharp9/xplat-tests

Xplat tests
Merge pull request #235 from knocte/simplify_build

Simplify build by removing GC tweaking logic
strong name dlls
Merge branch 'master' of https://github.com/fsharp/fsharp
Small changes to README.md
Remove prepositions, update name
Format corrections, correct name
Update continuous integration section
Fix text break, add link for NUnit
Correct markdown link
Shorten title, correct section case
Merge pull request #258 from brodyberg/edit_readme

Edits to README.md
update signed dlls