Omnisharp: smarter solution file finder

When loading the Omnisharp server, YCM tries to find a suitable solution
file to feed it. Instead of giving up when finding multiple solution
files, it now tries to find one named like the edited files' folder at
the solution level, e.g. if we have bla/Project.sln and we are editing
bla/Project/Folder/Whatever/File.cs, we use bla/Project.sln.
Check auto_stop_csharp_server when shutting down

Check auto_stop_csharp_server instead of auto_start_csharp_server when
shutting down
Unit test for Omnisharp's smarter solution finder
Unit tests for Omnisharp's smarter solution finder
Merge github.com:nop00/YouCompleteMe
Merge pull request #699 from nop00/fix-omnisharp-shutdown

Check auto_stop_csharp_server when shutting down
Updating to latest upstream Jedio

Relevant: https://github.com/davidhalter/jedi/issues/347
Adding the g:ycm_auto_trigger option

Toggling this option off turns off the identifier completer and the semantic
triggers.

Fixes #597
Add -include to INCLUDE_FLAGS

The -include flag forces the inclusion of a single file, and is used by
(at least) the Linux kernel's build system.
Small stylistic changes
Typing after <c-space> in g:ycm_auto_trigger works

We'd show the user the menu, but then we'd hide it as soon as the user tried to
type to filter the candidates.

Fixes #704
Merge pull request #703 from nixprime/master

Add -include to INCLUDE_FLAGS
Fix issue with omnifunc mode persisting

This can happen when the user inserts a candidate string like "operator[]" which
doesn't end with an identifier char. A very obscure bug, but a bug nonetheless.
Merge pull request #680 from nop00/master

Omnisharp: smarter solution file finder
Fix OmniSharp launch under Windows
Small refactoring

Use the dedicated function to check if we're running on Windows instead
of checking the platform directly.
Fix --system-libclang on Ubuntu/Debian
Merge pull request #713 from LeszekSwirski/fix-ubuntu-syslibclang

Fix --system-libclang on Ubuntu/Debian
Only notify about a server crash once

Fixes #715
Merge pull request #717 from blueyed/notify-about-crash-once-issue-715

Only notify about a server crash once