Refactor data upload: make 'statements' objects and consistently use them

[sjvrijn]

Fixes #37, (partially) addresses #43

We used to load the data into columnNames and rowValues, which were inconsistently passed around and stored through the code.

This PR:

• Creates a single global object window.INA, that all 'global' variables are now a part of, making it instantly clear when we're using a global variable somewhere
• Converts every column name to "Title Case", for consistency in rendering and validity checking. This makes the rowAttributes array obsolete.
• Adds an if-statement to only add an Id column if it is not yet present
• Changes column name checking to only check for missing columns from those we expect, ignoring any extra columns
• Creates statement objects at file upload time that map each column name to the corresponding value <== This gets rid of any fixed array order dependency and lets the rendering happen using the exact columns we want to use, regardless of their order in the file. This is what actually addresses issue #37
• Changes the session storage and table/chart re-rendering to use the plain columnNames array and the array of statements objects

As a result, this removes any global references to rowValues, since everything is replaced with the previously mentioned statements objects instead.