Allow table initializers in TOOL.ClientConVar and TOOL.ServerConVar

[Denneisk]

Extends the TOOL.ClientConVar and TOOL.ServerConVar to use tables to initialize the convars, in case developers want to extend the definitions in the tool easily.

The following presents the tables and their default values (these values are virtual and they're really just nil substitution).

Shared:

{
Value = "", -- string/number The default value of the convar
HelpText = "Tool specific <server/client> setting (<mode>)", -- string The help text of the convar
Min = nil, -- number The minimum value of the convar
Max = nil -- number The maximum value of the convar
}

Server:

{
Flags = FCVAR_ARCHIVE -- number/table The convar flags to initialize the convar with
}