added a check before executing SQL to associate an attribute type to an attribute category

- if attribute type was previously attached, SQL error was thrown
Prevent dashboard sort arrows displaying above context menu

z-index is too high so sorting arrows appear above the context menu on e.g. /index.php/dashboard/system/attributes/sets/category/1/
Resubmit: Addition of 'number' method/input type to Form Helper

Getting fed up of manually creating 'number' type fields in c5 forms! Now we can pass nifty 'min' and 'max' attributes to our input's $miscFields so decent browsers show a nice range clicker!
added convenience methods to select attribute controller to retrieve instance settings
Merge branch 'select-controller-settings-methods' of github.com:aghouseh/concrete5 into merge_append_1180_select_attribute
Change Private Properties to Protected

Change private properties to protected for overrides and new public
methods
combine two t-strings into one

better to translate it this way
Merge pull request #1188 from mkly/merge_append_1180_select_attribute

Merge append 1180 select attribute
Merge pull request #1189 from Remo/patch-48

combine two t-strings into one
Merge pull request #1103 from melat0nin/patch-8

Prevent dashboard sort arrows displaying above context menu
Merge pull request #1094 from aghouseh/add-check-to-attribute-category-association

added a check before executing SQL to associate an attribute type to an attribute category
Merge pull request #1155 from arcanepain/patch-1

Resubmit: Addition of 'number' method/input type to Form Helper