Allow development with `npm link`

[artzhookov]

This PR fixes problem when npm link is used to link nci package to the project working directory (for example nci-quick-setup). Problem is described below. Also I made some refactoring in app/config.js and app/index.js

I have such folders structure:

nci
|--- nci                  (npm link)
|--- nci-classic-ui       (npm link)
|--- nci-quick-setup      (npm link nci, npm link nci-classic-ui)

When I run nci inside nci-quick-setup folder I get:

~/projects/nci/nci/app.js:8
	if (err) throw err;
	         ^

Error: Cannot find module 'leveldown'
    at Function.Module._resolveFilename (module.js:325:15)
    at Function.Module._load (module.js:276:25)
    at Module.require (module.js:353:17)
    at require (internal/module.js:12:17)
    at Group.self.projects.ProjectsCollection.db (/home/webster/projects/github/nci/nci/app/index.js:72:20)
    at Group.<anonymous> (/home/webster/projects/github/nci/nci/node_modules/twostep/lib/twoStep.js:171:15)
    at next (/home/webster/projects/github/nci/nci/node_modules/twostep/lib/twoStep.js:159:9)
    at Group.done (/home/webster/projects/github/nci/nci/node_modules/twostep/lib/twoStep.js:30:16)
    at Group._fillSlot (/home/webster/projects/github/nci/nci/node_modules/twostep/lib/twoStep.js:52:8)
    at /home/webster/projects/github/nci/nci/node_modules/twostep/lib/twoStep.js:77:9

This happens because nci tries to require leveldown, but leveldown is a dependency of nci-quick-setup (custom db backend). Solving the problem is to do require call relative to cwd. I add import-cwd dependency and add method app.require that is used to require all external deps (db backend, plugins, proload.json).

[artzhookov]

Also I have another suggestion about development process:

1. remove devDependencies

    "nci-projects-reloader": "1.1.3",
    "nci-rest-api-server": "1.0.4",
    "nci-static-server": "1.2.0",
    "nci-yaml-reader": "1.2.1",

2. remove data folder
3. remove nodemon

This package should be clear as much as possible because it is the "core" package. For development process we should use separate package, that have nci in dependencies list (nci-quick-setup is a good candidate for this role). In this package nci and other nci-... packages could be linked with npm link (see my first comment).

[okv]

I need to think about this suggestions carefully =) I'll try to do that on next weekends.