Profile - Allow Customization of Field Labels

Users want to be able to customize the field labels displayed by Profile screens (create, search/listings, view).

1. Add new column to schema: civicrm_uf_field.label. Make this a varchar(255) size so folks can store 'questions', etc.

2. New form field in UF/Form/Field - "Field Label"
2.1 Use Jscript to populate this field with the 'default' field name as displayed in the "CiviCRM Field Name" <select> drop-down - this is triggered onchange of that <select> field.

3. Modify all Profile displays (civicrm/profile) to use the uf_field.label value

NOTE: Although we will default the field label value (using Jscript as described above) - we will allow this field to be saved as empty/NULL value - in which case NO field label is displayed for this profile field. This will allow folks to put un-labeled fields in a profile form which is sometimes desirable.