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 portable support for FSharp.Core

Although I have included Profile88 in the import and PropertyGroup
section it wont build on mono as this profile is not supported.

Only profiles 5,6,14,19,24,37,42,47,136,147,158 for .Net 4.0 and
7,49,78 for .Net 4.5

Conflicts:
	src/FSharpSource.targets
Added parenthesis around OR clause to make the condition logic clear.
Added parenthesis to make condition logic clear.
Merge pull request #239 from 7sharp9/master

Added portable support for FSharp.Core
Delete Microsoft.FSharp.target (lowercase)
renamed uppercase version
deleted uppercase version
renamed
renamed to uppercase versione
Merge pull request #243 from enricosada/fix_target

Delete Microsoft.FSharp.target (lowercase)
Merge pull request #244 from enricosada/fix_target2

Fix Microsoft.FSharp.Target (v2)
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
First version of the new Set and Map benchmarks.
Minor tidy up.