Microamp currents

Miscellaneous small fixes. The main change is to show current values in microamperes.

• Replace $(CHANNEL_NAME) macro in db files with $(P)$(R)$(CHANNEL). This allows inserting '#' in the correct place for hidden records
• Change current EGU to microampere
• Add record for switching all channels on or off
• Fix syntax error in calc record
• Add gitlab CI pipeline
• Reduce length of db file comments (dbformat rule DB011)