Define if Counter Frequency is triggered as fixed value or relavant to value defined during closing work order

DBC-1883

The user can specify if the counter frequency on the Work Order Plan should be calculated from fixed, or actual value.

From given example:

• choosing a Fixed option, when the Work Order is done, and the user will choose the counter reading on WO - the next triggered value for this WOP will be 300 + 100 so 400
• choosing an Actual option, when the Work Order is done, and the user will chose the counter reading on WO - the next triggered value for this WOP will be registered/chosen reading + 100 ** choosing/registering the counter reading 315 the next planned counter reading will be 415

Any existing counter frequencies before this new approach are treated as Actual.