Copy text improvements

- Translate non-translated strings in the accept transaction form
- Mention minimum fee and PayPal's fees in payment preferences info text
- Move text that has been proofread to getting started page
- Link to marketplace home page from getting started page
- Mailto link to support to getting started guide
- Mailto link to sales to getting started guide (custom domain)
- "No received messages" -> "No messages" in inbox
- Improve welcome email copy about "are you new to online marketplaces"
- Mailto link to support to welcome email
- Mailto link to support to left navi of admin panel
not sure if this kind of method makes this usage more clear. Looks like this is the only place to use this anywa?