Add command for doing bulk export of apps

[mountaindude]

Create an app-export command that exports apps to QVF files.

Should be possible to

• Prefix and suffix strings to each QVF file name
• Export with/without data
• Export to a customisable directory
• Specify a delay between each app export operation
• Select apps using app id and app tags

[mountaindude]

Released as part of v3.8.0