Add Up/Down Buttons to multiple editor GUIs

[WaitingIdly]

changes in this PR:

• add down buttons to the prerequisite and quest line editors.
• add up and down buttons to the task and reward editors.
• shrink the size of the buttons to 8x8 instead of 16x16, allowing both to fit stacked atop each other.
• make the buttons be on the far left side (avoids accidental deletions from misclicks).

supersedes #103