Reword prime directive to apply to the staff

The implication here is that the body of staff as a whole is bound by
the prime directive rather than any individual members of its staff
who are, of course, free to play on the server and take part in its
evolution as are any other players.
Remove the mention of contributor perks

Contributor perks are something that need deciding on but should not
fall under the scope of the prime directive.
Remove the mention of plugins

Whether or not the server is vanilla is orthogonal to the prime
directive -- besides which, the power of /spawn, /home and /sethome
(which are ultimately tools of convenience) already contravenes this
point.
Emphasise the importance of the PD

A substitution of 'must' for 'will' adds this emphasis.
Broaden the statement on exceptions

Generalising this to any cases where exceptions are necessary give us
scope for more changes while not affecting the spirit of the message.
Reword the staff's commitment slightly

The word 'undertake' here signifies an acceptance of responsibility
more than the previous wording.
Remove the phrase 'above all else'

As nice as this is as a turn of phrase, it is patently not true.
Change the tense of the commitment

The present tense implies it is something that will happen: the
reality is that it is -- or should be -- happening right now.
Simplify the naturality constraint

This is just a matter of shrinking the text without changing the
semantics.
Connect the sentences of the directive paragraph

This now flows so that the second section is an elaboration of the
first.
Remove some trailing whitespace
Reword to imply the staff as a whole
Merge pull request #3 from prophile/master

Reword the prime directive section