Merge branch 'hotfix/fix_columns_deletion'
Some updates in the NEWS.md
Merge branch 'develop' into release/staging
Shows 'unique field' message in text filters. Fixes 'This column empty' message showing too early
Shows empty message when the only value in the row is null
Resets filter state
Fixes spec
Don't show the error message on first load
Only return column types for CDB user tables list
Disable filters
Added function to get the column names of a table
Fixes error when importing csv files with the_geom columns
Removes export specs
Removes some legacy code and fixes user spec
Fixes importer issues

* Run VACUUM FULL on the importer and check user quota after that. We cannot
  run this operation on the table model because VACUUM FULL doesn't play well
  when there are opened transactions.
* Process the_geom column on csv files (previously you had to rename it to geojson)
Load functions in alphabetical order

Also prefixed 00- to CDB_UserTables since it's a dependency to other
functions
Remove queries and connection log entries from production and staging logs
load_cartodb_functions now accepts a list of files

Wihout any parameter it loads all the SQL files. It can receive an array
of SQL filenames in order to load them only
Sends the SQL query in the body with a PUT request
Stores the free_text filters + stores the list_view option + fixes specs