invoice_ui: @les to @log_entries
bootstrap_templates: update template to give more detailed example
invoice_ui: forgot a @les; change to @log_entries
key_value: put! should return nil
template_ui: use KeyValue for storing template id

This should fix #27.
version: bumpt to v1.2.0
attachment: make polymorphic in AR
issue: add attachments relation
migrations: add polymorphic alterations for attachment
innitdb: add polymorphic attachment migration
migrations/attachments: fix typo
innitdb: AR shouldn't be verbose in any case
cli_interface: remove attachment methods
issue_ui: add attachment methods
issue_ui: adapt attachment routines to new ui
issue_ui: re-enable attachments
issue_ui: rename attach commands
issue: add stringifying method for attachments
attachment: should have its own to_s logic
README: add docs badge