Finalised the implementation of the PID controllers

- Implemented 4 PID controllers

- Commands PIDx.INIT, PIDx.LIMITS, PIDx.PERIOD, PIDx.PARAMS, PIDx.SETMODE

- Function PIDx.COMPUTE

Addition of the max program size available in the console

- Shown when the program is loaded

Addition of the frequency information to the counters

- Function COUNTERx.FREQ

Addition of the command OPTION.MAC

- It is now possible to modify the MAC address

- Very useful for ESPNOW

Addition of the function CONVERT.xxx

- Generic conversion function

- Function CONVERT.DEGC_TO_F, CONVERT.F_TO_DEGC, CONVERT.TO_IEEE754, CONVERT.FROM_IEEE754

Improved the textbox$ function

- Now the variable is automatically updated as soon as the textbox loses the focus

Improved the WLOG command

Uploaded online 1.37 help

Several optimisations

- Modified the structure of the internal token table

- Improved the websocket send internal function

- Reduced firmware size

- fixed some internal snags