5544 nx schemas

1. Add following device classes:

• "ValveShutter"
• "OldKeithley6514"
• "OldKeithley6517"
• 'Adam6017'

2. Modify Channeltron to contain 'stage' and 'unstage' as it was at the OAESE.

3. Define nexus schemas for the following devices and decorate the device classes:

• Bruker
• Channeltron
• ChanneltronHV
• DCMEMIL
• Adam6017
• OldKeithley6514
• OldKeithley6517
• PGMSoft
• PGMHard
• PhotonShutter