Utility for writing to a register

What

This MR adds the tool/executable write-register and it works like this:

./bin/write-register -r <controller-config> -c <connectivity-config> <register-name> <register-value>

With register-name the name of a given register appearing in a front-end's JSON configuration file (with the names of all the registers) and <register-value> is the value to subsequently be written to that register.

The default behavior with the above command is to write the register to all chips in the provided connectivity file. Users can specify specific chips by providing either the -i or -n command line options. The -i option specifies the "index" of the desired chip in the "chips" list appearing in the connectivity file. For example,

./bin/write-register -r <controller-config> -c <connectivity-config> -i 2 <register-name> <register-value>

The -n option allows a user to specify a chip by name, where the name is the "Name" field accessible by an associated FrontEndCfg instance (given in the JSON configuration file for a given chip). For example,

./bin/write-register -r <controller-config> -c <connectivity-config> -n JohnDoe_0 <register-name> <register-value>

The full list of options can be seen by doing the following,

./bin/write-register -h