Add missing widget types

[juergenhoetzel]

This also fixes byte-compile-warnings:

In toplevel form:
powershell.el:789:1:Warning: defcustom for ‘powershell-location-of-exe’ fails
    to specify type
powershell.el:789:1:Warning: defcustom for ‘powershell-location-of-exe’ fails
    to specify type
powershell.el:794:1:Warning: defcustom for ‘powershell-log-level’ fails to
    specify type
powershell.el:794:1:Warning: defcustom for ‘powershell-log-level’ fails to
    specify type
powershell.el:799:1:Warning: defcustom for
    ‘powershell-squish-results-of-silent-commands’ fails to specify type
powershell.el:799:1:Warning: defcustom for
    ‘powershell-squish-results-of-silent-commands’ fails to specify type

[jschaf]

Thank you! Just merged.

[jschaf]

@juergenhoetzel would you be interested in commit access? I don't use powershell much these days so I'm happy to add you if you'd like.

[juergenhoetzel]

@juergenhoetzel would you be interested in commit access? I don't use powershell much these days so I'm happy to add you if you'd like.

@jschaf Feel free to add me to commit access. Although I also use the Powershell only occasionally.