Standardize token naming convention

We need to standardize the naming convention for token that is used in CiviCRM.

We use token replacement mechanism in following places:

1. Message template
2. CiviMail
3. Send Email to Contact Activity
4. Mailing labels

For 1,2,3 we use "

{contact.first_name}

" convention. but for 4 it is "

{first_name}

".

Check and fix all the places to use "

{contact.fieldname}

" convention. (eg.

{contact.street_address}

,

{contact.custom_1}

etc)

Also fix default values for Address formats.