calcJsonArray and update gradle

Fix json malformed for link(str, str) equations

Replace quotes before build the json by escaped quotes.

Fix default_value() numbers incompatibility (oxeanbits#14)

# Description 🗒️ 

This PRs converts integers to floats inside the `default_value()` evaluation, fixing the `default_value()` numbers incompatibility issue.

### Changes:

- [x] Update version to `0.2.4` for release 

last version published on jitpack `0.2.3`:
![DeepinScreenshot_select-area_20201009130255](https://user-images.githubusercontent.com/3251916/95605834-e401dc80-0a2f-11eb-9cd3-aecf28947e3e.png)

- [x] Fix issue associated with result of different types of number parameters

Now, this function is much more flexible to play with **integer** and **float** parameters.

For example...

```rb
parsec> default_value(1, 10)
Result (type: 'i'):
ans = 1

parsec> default_value(1, 10.0)
Result (type: 'i'):
ans = 1

parsec> default_value(1.0, 10)
Result (type: 'i'):
ans = 1

parsec> default_value(1.0, 10.0)
Result (type: 'i'):
ans = 1

parsec> default_value(1.5, 10)
Result (type: 'f'):
ans = 1.5

parsec> default_value(1.5, 10.0)
Result (type: 'f'):
ans = 1.5

parsec> default_value(1.5, 10.5)
Result (type: 'f'):
ans = 1.5
```

# The Bug 🐛 

![SLA error reason](https://user-images.githubusercontent.com/7637806/95136053-c97fe880-073b-11eb-8b88-a21901fba20c.png)

Reference: oxeanbits/equations-parser#31

Update version to 0.2.3

Update Parsec library with default_value() function (oxeanbits#11)

**Reference:** oxeanbits/equations-parser#29 (comment)

# Description

- [x] Increase version from `0.1.3` to `0.2.1` due addition of new feature (in release tags, the version is already 0.2.0)
- [x] Adda new function on the library.:

```C
default_value(value, standard)
```

If the **value** is `NULL`, the result of this function is the **standard**, otherwise, the result is the **value**.

This function accept both `integer`, `float`, `string` and `boolean` types. (C++ overloading for the win)

Some success test samples: ✅

```C
default_value(10, 1)
default_value(NULL, 1)
default_value(10.4, 1.01)
default_value(NULL, 1.01)
default_value("filled", "default")
default_value(NULL, "default")
default_value(false, true)
default_value(NULL, true)
```

Some failure test samples: 🚫

```C
default_value(1, 4.5)
default_value(4.5, "string")
default_value("string", true)
default_value(true, 1)
```

This PR also add a new constant on the lib: the `NULL` constant.

Update Parsec library with add_days() and mask() functions (oxeanbits#10

)

Display current_date() with the right format (oxeanbits#9)

Add diff hours func (oxeanbits#8)

Update parsec native with number to string formulas (oxeanbits#7)

Update gradle version (oxeanbits#6)

* Updated gradle version
* Removed .idea folder