- Exclude artificial headers
- Avoid extra '#' operations
- Do not insert ONCE_RECEIVED if MTA has not resolved the first received
(#2190)

This reverts commit f552edd887.

Conflicts:
	src/plugins/lua/antivirus.lua
	src/plugins/lua/asn.lua
	src/plugins/lua/dcc.lua
	src/plugins/lua/dmarc.lua
	src/plugins/lua/emails.lua
	src/plugins/lua/forged_recipients.lua
	src/plugins/lua/greylist.lua
	src/plugins/lua/hfilter.lua
	src/plugins/lua/ip_score.lua
	src/plugins/lua/maillist.lua
	src/plugins/lua/mime_types.lua
	src/plugins/lua/multimap.lua
	src/plugins/lua/once_received.lua
	src/plugins/lua/ratelimit.lua
	src/plugins/lua/rbl.lua
	src/plugins/lua/replies.lua
	src/plugins/lua/rspamd_update.lua
	src/plugins/lua/trie.lua
	src/plugins/lua/whitelist.lua

Issue: #661
Reported by: @FelixSchwarz

Issue: #602
Reported by: @AlexeySa

2016-02-17 13:00:50 #58424(normal) <a41bdc>; task; lua_metric_symbol_callback: call to (ONCE_RECEIVED) failed: /usr/local/share/rspamd/lua/once_received.lua:82: bad argument #1 to 'lower' (string expected, got nil); trace: [1]:{[C]:-1 - lower [C]}; [2]:{/usr/local/share/rspamd/lua/once_received.lua:82 - <unknown> [Lua]};

- Fix priority for `good_hosts`
- If a good host has been found do not add once_received symbols
- Fix priorities for strict once_received
- Add ability to whitelist IP addresses

* Add ability to resolve ip in once_received plugin to avoid temporary DNS fails of SMTP resolving

* Provide compatibility for lua plugins for old versions of rspamd

 - now symbols inside metrics definition must be inside rules as well
 - symbols may be virtual (e.g. when module can insert several symbols inside callback)
 - symbols may be pure callbacks (when symbol's name is unknown and depends on conditions)
* Module 'emails' is removed as it is not used in the current rspamd
MANY fixes to sample config files

* Add ability to output colored messages for file and console loggers