* [Commands] Add entity variable commands
# Commands
- Add `#clearentityvariables` to clear all entity variables from yourself or your target.
- Add `#deleteentityvariable [Variable Name]` to delete an entity variable from yourself or your target.
- Add `#setentityvariable [Variable Name] [Variable Value]` to set an entity variable for yourself or your target.
- Add `#viewentityvariables [Search Criteria]` to view your or your target's entity variables.
# Notes
- `#setentityvariable` can use multi-word names/values by using double quotes like `#setentityvariable "Test Variable" "Test Value"`.
- `#viewentityvariable` does not require a search criteria, not using one shows all entity variables on yourself or your target.
* Update viewentityvariables.cpp
* Unnecessary parameter.
* Consolidate commands.
* Update entityvariable.cpp
* Update command.cpp
* Proper arguments.
* [Feature] Add Experience Gain Toggle.
# Perl
- Add `$client->IsEXPEnabled()`.
- Add `$client->SetEXPEnabled(is_exp_enabled)`.
# Lua
- Add `client:IsEXPEnabled()`.
- Add `client:SetEXPEnabled(is_exp_enabled)`.
# Commands
- Add `#exptoggle [Toggle] - Toggle your or your target's experience gain.`.
# Notes
- Allows operators to turn on/off a player's experience gain individually without changing their rule values.
- The command allows operators to give players access to the command to disable their own experience gain.
