Add factory reset function

[sfe-SparkFro]

All modules (should) support the factory reset AT command:

+UFACTORY:<fs_op>,<nvm_op>

Could be useful in case a user gets their module all twisted up. Requires a reboot to take effect.

Looks like the following values can be used for <fs_op>:

• 0 - Does nothing
• 1 - Depends on module
  • SARA-R5 - "Not supported"
  • LARA-R6 - "Deletes all user files previously stored with "USER" tag"
• 2 - Depends on module
  • SARA-R5 - "All files stored in FS are deleted"
  • LARA-R6 - "Not supported"

And for <nvm_op>:

• 0 - Does nothing
• 1 - Depends on module
  • SARA-R5 - "Not supported"
  • LARA-R6 - "Deletes all modem profiles" and a second reboot is required
• 2 - Depends on module
  • SARA-R5 - "Restores the NVM to the factory-programmed configuration"
  • LARA-R6 - "Restores the UART interface and +UPSV AT command settings to the factory-programmed setting"

[PaulZC]

Some relevant code here and here