Remove password option

Remove password option which is no more available with api-v2
Add a -Q option to perform complex saving requests

Add the following option: -Q REQUEST, --request=REQUEST

Save posts following the pattern TYPE:TAGS. TYPE can be any, text,
quote, link, answer, video, audio, photo, chat; TAGS can be omitted.
TAGS can be comma-separated values, REQUEST semicolon-separated
patterns. Example: "-Q any:personal;quote;photo:me,self"

This is a squashed commit of the following:

commit 908a74b734f342a1515f6da085d8a72e32bfa67a
Author: WyohKnott <clare.tor86@gmail.com>
Date:   Mon Oct 27 14:35:31 2014 +0100

    Convert -T and -t options to the request syntax

    - the -t and -T options callbacks convert the parameters to the request
      syntax
    - a new function request_append merge the filters set by -t, -T and -Q
      callbacks
    - requesting an entire type supersedes any tag based filter. For
      example, using "-T text -t personal" will save all posts tagged
      personal and all text posts.

commit 3ccadc5e1b9457052b5e6b1f6f72be5621c4e5d1
Author: WyohKnott <clare.tor86@gmail.com>
Date:   Mon Oct 27 11:58:03 2014 +0100

    Simplified options.request callback

commit e725998a047f561891d5c221c0f1297fd8905883
Author: WyohKnott <clare.tor86@gmail.com>
Date:   Sun Oct 26 11:03:51 2014 +0100

    Add a -Q option to perform complex saving requests
tumblr_backup: simplify the -Q handling
tumblr_backup: simplify -Q syntax

WARNING: This commit breaks existing scripts that use -Q.

Change the TAG separator to colon, and the rule separator to comma.
The new rule syntax is now TYPE:TAG:TAG:…,TYPE:TAG:…,….

This is a win because of two factors:

  - The semicolons between the rules had to be quoted in typical Unix
    shells.

  - Using the same separator inside one rule makes parsing the rule
    easier.

In effect, the -T and -Q options are now equivalent. But don't tell
anyone, because the manual doesn't say so ;-)

Also add documentation for -t and -Q.
Merge branch 'gh-39' into api-v2