TEST: Allow runspace initial session state to be configured for TestHost.
Allow initial session state variables to be accessed from runspace.
Make cmdlets defined in initial session state available to runspace.
REFACTOR: Remove duplicate code when loading cmdlet information.
Merge pull request #147 from mrward/initial-session-state

Initial session state - variables and modules
Allow cmdlet to invoke a script.

Implement PSCmdlet.InvokeCommand.InvokeScript()
Merge pull request #148 from mrward/invoke-script

Allow cmdlet to invoke a script.
Implement AST for param block.
Implement AST for param block default values.
Bind arguments by position to script parameters.
Use default script parameter value if argument is not passed.
Merge pull request #149 from mrward/param-block

Binding arguments to script parameters.
Allow static members to be called from type stored in variable.

Supports the following statements:

[Environment]

$path = [System.IO.Path]
$path::GetDirectoryName($project.FileName)
REFACTOR: Remove duplicate code when visiting static members.
TEST: Use TestCase in -eq tests.
Support using $null, bools and strings with -eq operator.
Make -eq case insensitive for strings.
Implement -ge for integers.
Implement -not operator.
Implement -match operator.