initSymbol will load a symbol and run user-defined functions to pre-process the symbol's data
before constructing indicators.
initSymbol(strategy, symbol, ...)an object (or the name of an object) of type 'strategy' to add the init function definition to
symbol
any other passthrough parameters
The custom initialization must be defined as named list containing
function name
list of arguments
TRUE or FALSE
and included as the slot init_symbol of the strategy object.