MERGE W/ e68f28ec
introduce graphitize tool for generating PDF graphs from data

This change introduces graphitize, a helper tool for generating PDF
graphics that visualize the development of prices over time. Along with
the act of drawing candlesticks with the opening and closing prices as
well as marks for the lowest and highest prices for the respective
interval, it is also able to display EMA 10 and EMA 20 trendlines as
well as the intersection points between these two lines.
This tool is not meant to be interactive in any way, its mere goal is to
produce a static PDF file that can be used to visualize the data from a
certain point in time to get a better understanding of what was going
on.
make use of matplotlib rc file in graphitize tool

It is possible that matplotlib is used in more places in the future
where graphs similar to those produced by graphitize are to be drawn.
To that end, and in order to remove stylistic references from the code
where possible, common style settings can be placed in a configuration
file that can be shared.
This change introduces such a configuration file and adjusts graphitize
to expect it to be provided along with its source code file.
add support for drawing multiple data sets

With this change graphitize accepts multiple input files and visualizes
them all, putting the output into a single file. The main hurdles that
had to be coped with here are the correct calculation of the candlestick
width which has to be specified as "fraction of a day". Apparently, this
is not completely true and an additional correction factor is required
(or perhaps my thinking/calculation is flawed).
The other bit worth mentioning is the creation and arrangement of
subplots -- one for every input file to visualize. A custom arragement
scheme was implemented because the default one did not produce the
anticipated result.