feature : core add-on ofxAssets

hey all!

in a few of my addons i build an asset register to handle:

• images
• shaders
• fonts

The idea is common. That on program start (and whenever you call ofxAssets::rescan()), it scans the data/ folder for assets and builds the dictionaries.

e.g. if my folder structure is like

data/landscape.png
data/phong.vert
data/phong.frag
data/blur.frag
data/verdana.ttf

or sometimes i do...

data/images/landscape.png
data/shaders/phong.vert
data/shaders/phong.frag
data/shaders/blur.frag
data/fonts/verdana.ttf

I can then access these from anywhere in my app as long as i'm including the ofxAssets header:

#include "ofxAssets.h"
using namespace ofxAssets;

void testApp::draw() {
    shader["blur"].begin();
    image["landscape"].draw(10,10);
    shader["blur"].end();
    font["verdana"].drawString("is this API correct?", 10, 10);

    //or if i don't want to add the using namespace clause
    ofxAssets::shader["phong"].setUniform3f("position", myVec3);
}

I'd like to see this as a core add-on as I think it's rather universally useful, the code is beginning to be duplicated in different addons and the API is simple enough to avoid much deliberation. (spoke to soon)

Start by reviewing the proposed ofxAssets API in the issue, especially ofxAssets.h and ofxAssets::rescan(). Determine how a core add-on should scan the data/ folder and expose images, shaders, and fonts through the shown dictionaries. Done means the behavior and API are agreed, implemented, and covered by appropriate project tests.