Requests for comment/Ditch crappy API formats

The initial goal of this RFC was the deprecation of several silly API output formats. However, this was generally achieved as part of the larger Requests for comment/API roadmap RFC, so I would like to concentrate on a clearer timeline for their complete removal.

Current state
Here's the breakdown of API formats requested by users from Wikimedia sites during June 19, 2014: 375079448	json 34750831	xml 13068687	php 243625	xmlfm 71337	txt 62549	jsonfm 41158	text/x-wiki 34458	dbg 24460	yaml 7532	txtfm 34	yamlfm 31	dbgfm 28	none 25	rawfm 23	dump 22	phpfm 22	wddxfm 22	dumpfm 18	wddx 4	html 4	jsonf 3	jsonp 3	j 2	atom 2	raw 2	text 2	csv 2	PHP%20print_r 1	wdxfm 1	default 1	pjson 1	xhtml 1	XML 1	plain 1	htmlfm 1	yamfm 1	xml%27 1	xm%20l 1	js 1	jsonaction%3Dquery 1	json%0D%0A 1	xml%27,%200,%20true 1	xml%27,0,true 1	jaon 1	xmuslfm

Proposal
Set a clear date when a format should die. Contact major users of a format in advance to ensure they move off it, e.g..

Proposed timeline:
 * 6 months for WDDX and dump.
 * 12 months for YAML, dbg and txt.