Allow users to add fields

[bronwyncombs]

There are several table extension requests for various reasons:

• Add boolean field(s) to CE table #8061
• Add fields to Storage table #7955
• Add fields to TreatmentEvent Table #7954
• Add fields to VoucherRelationship table #7953
• Add precision date fields in Accession form #5970
• Add new fields to the Reference Work table #5818
• Add fields to Taxon table for better full name generation #5920

We could consider allowing users to add fields to a table's schema

Note Paul Blom's remark in 890

With all the flexibility now in 7.12 should I be able to add a field to a table? Specifically I want to add a Boolean field to the Collecting Event table.