#196 Add builtin EQ

[Samuel Miller]

When anayalising audio, it's often helpful to highlight instruments in specific frequency ranges. I suggest you add a builtin EQ to be displayed in the tab on the right--either via a button next to the pan/volume or as a simple UI right above since there is plenty of the space in the lower part of the tabs Perhaps, in the preferences one could specifity what type of EQ to display--e.g., band or parametric. Currently, one has to find, download and install an EQ plugin and is akward to use.