support spreadsheet parsing

[seiyria]

this will first require #26 to be done. afterwards, a syntax for iterating over the rows in a google spreadsheet will need to be thought of. that depends entirely on the format of the data.

possibly:

• publish to the web as xslx
• use js-xslx (https://github.com/SheetJS/js-xlsx)
• take the xslx link
• use papa parse to parse the resulting csv data (http://papaparse.com/)

or:

• use tabletop
• store the data whenever the resource is added (or on page load) and have a promise for when all resources are loaded
• add a refresh button for resources like this that can force a hard refresh
• store data in firebase?

Also, add a loading indicator for loading resources.

possibly require a for-in loop with the sheet names to parse?

loop =  <sheet> in { "Mage", "Cleric", "Warrior", "Thief" }
  loop = <row> in <<resourceId>>:<sheet>
    loop = <card> to <row_Quantity>
      text = <card_index>, "<row_Name>", 0, 0, 0, 0
    endloop
  endloop
endloop

add a new directive that lets you set a new card index and use it by binding a variable to the scope because math is hard and dumb