Should create plugin folder for agent if none is present

[Calnoras]

Agent should automatically generate a folder for plugins when none is present and is allowed:

StackTrace:
Unhandled exception. System.IO.DirectoryNotFoundException: Could not find a part of the path '/home/sascha/source/AyBorg/src/Agent/bin/Debug/plugins'.
at System.IO.Enumeration.FileSystemEnumerator1.CreateDirectoryHandle(String path, Boolean ignoreNotFound) at System.IO.Enumeration.FileSystemEnumerator1.Init()
at System.IO.Enumeration.FileSystemEnumerable`1..ctor(String directory, FindTransform transform, EnumerationOptions options, Boolean isNormalized)
at System.IO.Enumeration.FileSystemEnumerableFactory.UserDirectories(String directory, String expression, EnumerationOptions options)
at System.IO.Directory.InternalEnumeratePaths(String path, String searchPattern, SearchTarget searchTarget, EnumerationOptions options)
at AyBorg.Agent.Services.PluginsService.Load() in /home/sascha/source/AyBorg/src/Agent/Services/PluginService.cs:line 54
at Program.

$(String[] args) in /home/sascha/source/AyBorg/src/Agent/Program.cs:line 82
at Program.(String[] args)