Adds people vars ($who, $to, $someone) and pronoun vars ($he, $her, $itself, etc.)
Implements proper variables, closes #19
Moves the reply module into its own project.
Moves the in-memory data store logic into its own project.
Moves the variables module into its own project.
Moves the people module into its own project.
Adds a new project/module for simple response handlers.
Fixes up the current unit tests and their structure.
Moves the data access layer interfaces to its own project.
Fixes broken references.
Removes more unused references.
Fixes the Driver csproj.
Merge branch 'feature/move-modules-into-separate-projects' into feature/add-remember-functionality

Conflicts:
	Gambot.Tests/Gambot.Tests.csproj
Removes unused directives and moves the base class to the root of the Modules filter.
Renames GrandMessageHandler to MessageDispatcher and extracts an interface.
Renames Variables to VariableHandler and extracts an interface.
Adds the IModule class to Gambot.Core.
Adds an AbstractModule and PeopleModule and changes the access visibility of the handlers inside of the module to internal.
Adds a ReplyModule and changes the access visibility of the handlers inside of the module to internal.
Adds a SimpleModule and changes the access visibility of the handlers inside of the module to internal.