Move all static variables, labels and messages into translation file

[ParthivPatel-BTC]

1) Static variables, labels, messages should be in separate translation file 2) Values should have proper hierarchy. For e.g.

clients:
    captions:
        page_header:
            new: 'New Client'
            edit: 'Edit Client'
   messages:
       created: 'New client created successfully.'
       updated: 'Client updated successfully.'
common:
    button:
        save: 'Save'
        cancel: 'Cancel"

[amitpatelx]

@ParthivPatel-BTC @PragatiDoshi-BTC make sure you group everything properly.

e.g., Most common labels like Save, Email etc would go under a common session. Labels/messages specific to Invoice would go under invoice.