Terrible handling of initLen / minLen and variable length characteristics.

[Timmmm]

(This is a duplicate of ARMmbed/ble#93 as it affects both projects.)

See: https://devzone.nordicsemi.com/question/34390/no-ble_gatt_hvx_notification-under-20-bytes/?answer=55637#post-id-55637

Basically there are two problems:

1. The GattCharacteristic initLen parameter is randomly named minLen too. If you follow the code all the way through it actually does two things - it is the initial length (not minimum), and it determines whether the characteristic is variable length or not.
2. The characteristic for nRF51822 code is only variable length if initLen != maxLen. This is really stupid because you might want the initial length to equal the maximum length but still have variable length. It also isn't documented anywhere.

I suggest the following solution:

1. Add extra constructors with an extra parameter: bool variableLength.
2. Name initLen to be initLen everywhere consistently (and not minLen).
3. Deprecate the old constructors.

[rainierwolfcastle]

ARM Internal Ref: IOTSFW-1156

[andresag01]

I believe this has been solved in 3fb32e1