On some machines (including Team City), GetFiles caused a test failure

FileLocator.LocateInProgramFilesFolder() started failing because Directory.GetFiles() throws an exception
if even one of the Program Files child directories doesn't allow you to search it.
Merge pull request #116 from sillsdev/Fix_FileLocator.LocateInProgramFilesFolder

On some machines (including Team City), GetFiles caused a test failure
Ignore DBus generated exceptions in USB scanning

These seem to happen on occasion for no particular reason, but
shouldn't kill the program.  See https://jira.sil.org/browse/WS-226
for an example of such a crash.  Several other issues involve such
exceptions, but each one seems to be a different exception.
Merge pull request #115 from sillsdev/Fix-WS-226

Ignore DBus generated exceptions in USB scanning
Fix failing tests on Linux

A recent change was too Windows specific.  This fixes that
problem, essentially by reverting the change functionally
#if __MonoCS__.
Merge pull request #117 from sillsdev/Fix-Failing-Linux-FileLocator-Tests

Fix failing tests on Linux
Message cut off in Mono because the label is not resizing correctly
Merge pull request #118 from phillip-hopper/BL-303

Recycle message cut off in Mono because the label is not resizing correctly
Fix a settings saving crash observed in the wild

* If the SerializedValue we are given comes up null when saving
  a string then save out an empty string instead of crashing.
Correct PalasoUIWindowsForms.Tests.csproj to have 2-space tabs

Visual Studio generates this file with 2-space tabs, so that is
what we need to have in the repo.  Additionally, before this
change, the indentation was a mix of tabs and spaces.
Add ability to block by acquiring and releasing a unique token
Use a lock file rather than a named mutex

Making named mutexes work in mono requires enabling shared memory
which is not an ideal solution.
Merge pull request #121 from andrew-polk/master

Correct PalasoUIWindowsForms.Tests.csproj to have 2-space tabs
Merge pull request #120 from sillsdev/FixSettingsCrash

Fix a settings saving crash observed in the wild
Various improvements based on review feedback
Merge pull request #122 from andrew-polk/BL475_BlockOnToken

Add ability to block by acquiring and releasing a unique token (BL-475)
Correct Palaso.csproj to have 2-space tabs

Visual Studio generates this file with 2-space tabs, so that is
what we need to have in the repo.  Additionally, before this
change, the indentation was a mix of tabs and spaces.
Merge pull request #124 from andrew-polk/master

Correct Palaso.csproj to have 2-space tabs