digest+m_auth: Allow a domain in the digest username.

Before this patch, a domain in the digest username was allowed:

    Digest username="abc@domain", realm="domain"

but only if the domain is equal to the realm. This was introduced in
a92bf789 (Juha Heinanen, Mar. 29 2006).

The SIP spec. doesn't mention any such restriction.

This patch undoes that commit and makes sure the whole username is used
when authenticating through `pv_www_authorize` and `pv_proxy_authorize`.
That makes the following valid:

    Digest username="abc@domain", realm="something different"
dispatcher: enhance MI ds_list command
 - print socket if set
 - print attr if set
Fixed bogus test over the presence of a request route. This was generating bogus warning messages to the logs, but without any negative impact over the actual processing.
Credits go to rrb3942 on GITHUB
Closes issue #162
cachedb_mongodb: fix BSON_DATE conversion
Fix NULL pointer deref. in "acc_db_request" when "db_url" is not set
cachedb_mongodb: use constants for oip size
cachedb_mongodb: retieve ObjectId _id as string
cachedb_mongodb: fix sorting results for mongo queries
cachedb_mongodb: handle _id based queries
cachedb_mongodb: complete previous commit - handle _id based queries
improve docs
Proper reporting for invalid module parameter types
allow route_to_gw() to receive a list of gw IDs (instead of only one) - the list is a comma separated list of gw IDs
docs updated for route_to_gw()
Job timeout for the 'exec' module

* the "time_to_kill" parameter now works for all "exec_*" commands
* improved overall documentation and usage examples
mod_fix: new helper fixup function that returns string and/or int value from a gparam_t
registrar: Fix harmless compiler warning
dialplan: move the "attrs" pvar into the "dp_translate" param list

* simplifies the scripting logic
* more efficient - it is now a local option, as opposed to a global one
dispatcher: add ability to handle string PVs for ds_select_dst/domain
Fix issue introduced in commit "23174d2629c"