Should use -Force when importing plugin modules

Description

When using PoshBot in an interactive shell, the module remains loaded in the session even if a bot instance is stopped and later started. Plugin modules are imported into PoshBot's scope.

This means that after a plugin module has been imported once, subsequent calls to Import-Module will not do anything. If new plugin functions have been added PoshBot will not know about them after stopping and starting the instance.

Using -Force ensures that modules are always (re)loaded from disk.

Related Issue

#117

Motivation and Context

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.