[Minor] Fix --var in rspamd CLI arguments

We can add varaibels on the command line after argument or using --var parameter.
When --var is used, an assertion is triggered:

   ./rspamd.install/bin/rspamd --var LOGDIR=/tmp/
   (rspamd:7171): GLib-CRITICAL **: g_hash_table_insert_internal: assertion 'hash_table != NULL' failed

The hash table is not initialized, because the table is initialized after
the argument parser.

This patch initialize the hash table on demand.

Note: the patch is tested on 1.9 version and not on master, because I can't compile the master branch.

Note: I suggest to backport the patch on 1.9 version

[WebUI] Add auto-refresh interval settings

[Fix] metadata_exporter default formatter

[Minor] Remove leftover CSS rule set

[Test] URL compose map

* [CritFix] Fix parsing of the content type attributes
* [Feature] Clickhouse: Add extra columns support
* [Feature] Rbl: Add url_compose_map option for RBL rules
* [Fix] 'R' flag is for all headers regexp
* [Fix] Allow to reset settings id from Lua (e.g. because of the priority)
* [Fix] Avoid collisions in mempool variables by changing fuzzy caching logic
* [Fix] Avoid strdup usage for symbols options
* [Fix] Do not trust stat(2) it lies
* [Fix] Filter all options for symbols to have sane characters
* [Fix] Fix all headers iteration
* [Fix] Fix allowed_settings for neural
* [Fix] Fix listen socket parsing
* [Fix] Fix maps expressions evaluation
* [Fix] Fix sentinel connections leak by using async connections
* [Fix] Fix smtp message on passthrough result
* [Fix] Fix tld compositon rules
* [Fix] Fuzzy_storage: Do not check for shingles if a direct hash has been found
* [Fix] Lua_mime: Do not perform QP encoding for 7bit parts
* [Fix] Neural: Distinguish missing symbols from symbols with low scores
* [Fix] Support listening on systemd sockets by name
* [Project] Add lua_urls_compose library
* [Project] Allow to set a custom log function to the logger
* [Project] CDB maps: Start making cdb a first class citizen
* [Project] Clickhouse: Add extra columns concept
* [Project] Fix urls composition rules, add unit tests
* [Project] Unify cdb maps
* [Rework] Logger infrastructure rework
* [Rework] Refactor libraries structure
* [Rework] Rework SSL caching
* [Rework] Update snowball stemmer to 2.0 and remove all crap aside of UTF8

Signed-off-by: Vsevolod Stakhov <vsevolod@highsecure.ru>

[Minor] Fix metadata_exporter extra mail recipients

Issue: #3254

Issue: #3254

Issue: #3248, #3268

Issue: #3270

Issue: #3267