Make codebase IDE-independent

[mountain]

Hi, folks,

Let's start from this PR, it makes the codebase IDE-independent.

Mingli

[digama0]

Why the deletions? Those files contain project preferences that might be useful for anyone browsing or editing the project using Eclipse. Perhaps they aren't useful for everyone, but I see no reason to delete them on that basis. On the contrary I would rather see preference files for any IDE that is in use by developers on the project (at least for preferences that are useful generally, like tab settings and formatting, as opposed to color themes or fonts).

[mountain]

for the tab setting and other editor settings, maybe we can adopt a editorconfig file
https://editorconfig.org/

It is supported by VSCode, IntelliJ, Eclipse(by plugin) and other editors.

But the .classpath file, I can not find a IDE-agnostic solution...