Default should always be stable

[rahul286]

I ran

fm create erp.localhost --apps erpnext --apps hrms

and got dev versions for erpnext and hrms

+------------------+--------------------------------------------+
| Bench Apps       | App               | Version                |
|                  | ------------------+----------------------- |
|                  | frappe            | 15.8.1                 |
|                  | ------------------+----------------------- |
|                  | erpnext           | 16.0.0-dev             |
|                  | ------------------+----------------------- |
|                  | hrms              | 16.0.0-dev             |
+------------------+--------------------------------------------+

[Xieyt]

Considering this as an enhancement, each FrappeVerse app will automatically default to its stable branch. This will be hardcoded into the codebase and adjusted when necessary.

[Xieyt]

Added stable app and branch mapping for apps: Frappe, HRMS and ErpNext to version-15 in #115.