accdb: extract the multi-arg CLI search code

This is cleaner and will also be needed for a bugfix.
accdb: fix filters with spaces in 'show' &c.
accdb: add missing 'UUID' search op; fix error message
accdb: move some functions into Filter
accdb: move compile_pattern() into PatternFilter
accdb: wrap changeset functions in a class
accdb: use a proper constructor
accdb: remove unused function
accdb: show parsed filter in 'grep' again
accdb: consolidate $DEBUG checks
accdb: filter \deleted when loading, not grepping
accdb: remove comment
accdb: fix an Attribute leftover
accdb: fix extra argument from long ago
accdb: make sure 'name' is sorted first