Remove general.yml Admin section

Many items underneath are not administration settings
Add note about default config in general.yml

Default settings are taken from lib/configuration.rb if not set by the user.
Make csv import fields a class attribute that can be overriden
Fix test failures in PublicBody overrideable CSV import specs
Add documentation to general.yml parameters

Also available at http://alaveteli.org/docs/customising/config
Add default INCOMING_EMAIL_PREFIX

All our examples use the 'foi+' prefix so lets make this the default. If
people _really_ want no prefix, they can change the setting to ''. This
will probably cover the more general cases.
Emphasise suggestion to change emergency admin details
Don't set non-default value for USE_GHOSTSCRIPT_COMPRESSION

We don't set this to true as a default so don't supply the non-default
to new installs.
Set default MAX_REQUESTS_PER_USER_PER_DAY

We supply a default example for MAX_REQUESTS_PER_USER_PER_DAY so we
might as well set it as default and allow the user to tune if they
dislike the default.
Add default MTA_LOG_PATH

We default MTA_LOG_TYPE to exim so we can set the default log path too
Use default setting for MINIMUM_REQUESTS_FOR_STATISTICS

Defaults to 100 so use this in the example config
Provide sensible defaults for emails

Provide something that at least has a chance of existing and might get read
Update default RESPONSIVE_STYLING
Merge branch 'issues/1668-general-config-docs' into rails-3-develop
Update translations
Update translations
Update translations
Use null values for general settings

mySociety’s internal deployment system requires these to be
set in some capacity (even if the value is null).
Merge branch 'general-null-values' into rails-3-develop
Merge branch 'master' into rails-3-develop

Conflicts:
	locale/cy/app.po